On 01/12/2020 06:06, Herbert Xu wrote:
On Tue, Dec 01, 2020 at 04:42:03PM +1100, Herbert Xu wrote:
Nevermind, I see that the script has been modified to use bash.
I can reproduce the problem now so it's all good.
OK the problem is this:
sh -c 'sleep 1d& exec $MYSHELL -c "sleep 1& wait"'
You can replace MYSHELL with whatever shell you want to use.
Essentially dash will now wait for all children, even ones that
were created prior to its existence, however, bash only waits for
children that it created directly.
FWIW ksh exhibits the same behaviour as dash and I think there
is nothing wrong with this.
POSIX says:
"If the wait utility is invoked with no operands, it shall wait
until all process IDs known to the invoking shell have terminated and
exit with a zero exit status."
I would say that child processes that were created before dash was
started do not have process IDs known to dash.
So the problem is really in the parent of this shell, which appears
to be bash:
bash -c set -e; export USER=`id -nu`; . /etc/profile >/dev/null 2>&1 || true; . ~/.profile >/dev/null 2>&1 || true; buildtree="/tmp/autopkgtest-lxc.is4n6xxr/downtmp/build.f2G/real-tree"; mkdir -p -m 1777 -- "/tmp/autopkgtest-lxc.is4n6xxr/downtmp/timedated-artifacts"; export AUTOPKGTEST_ARTIFACTS="/tmp/autopkgtest-lxc.is4n6xxr/downtmp/timedated-artifacts"; export ADT_ARTIFACTS="$AUTOPKGTEST_ARTIFACTS"; mkdir -p -m 755 "/tmp/autopkgtest-lxc.is4n6xxr/downtmp/autopkgtest_tmp"; export AUTOPKGTEST_TMP="/tmp/autopkgtest-lxc.is4n6xxr/downtmp/autopkgtest_tmp"; export ADTTMP="$AUTOPKGTEST_TMP"; export DEBIAN_FRONTEND=noninteractive; export LANG=C.UTF-8; export DEB_BUILD_OPTIONS=parallel=2; unset LANGUAGE LC_CTYPE LC_NUMERIC LC_TIME LC_COLLATE LC_MONETARY LC_MESSAGES LC_PAPER LC_NAME LC_ADDRESS LC_TELEPHONE LC_MEASUREMENT LC_IDENTIFICATION LC_ALL;rm -f /tmp/autopkgtest_script_pid; set -C; echo $$ > /tmp/autopkgtest_script_pid; set +C; trap "rm -f /tmp/autopkgtest_script_pid" EXIT INT QUIT PIPE; cd "$buildtree"; export AUTOPKGTEST_NORMAL_USER=; export ADT_NORMAL_USER=; chmod +x /tmp/autopkgtest-lxc.is4n6xxr/downtmp/build.f2G/real-tree/debian/tests/timedated; touch /tmp/autopkgtest-lxc.is4n6xxr/downtmp/timedated-stdout /tmp/autopkgtest-lxc.is4n6xxr/downtmp/timedated-stderr; /tmp/autopkgtest-lxc.is4n6xxr/downtmp/build.f2G/real-tree/debian/tests/timedated 2> >(tee -a /tmp/autopkgtest-lxc.is4n6xxr/downtmp/timedated-stderr >&2) > >(tee -a /tmp/autopkgtest-lxc.is4n6xxr/downtmp/timedated-stdout);
For some reason this is causing the final two tee's to be created
as children of debian/tests/timedated rather than the bash shell.
This is because of the same optimisation that dash also has, where it
tries to avoid creating a subshell for the last command in a list when
it can just exec() without a fork() instead. A minimal example without
an explicit exec is
bash -c 'dash -c ": & wait" <(sleep 1d)'
Cheers,
Harald van Dijk
